The majority of local recurrences occur within the first few years of treatment (85% within five years). Of these, 1 to 2 percent first appear after 10 years of tumor-free survival. Therefore, regular review, including mammography, is a crucial measure for early diagnosis of regenerative cancer in the contralateral breast in 15-20% of patients. Some patients undergo conservative surgery, such as local excision of the lump, which is not difficult to cure even if it recurs, and these patients deserve close follow-up review. There are many factors related to the prognostic factors of breast cancer, among which the main ones are related to the extent of tumor invasion and pathobiological characteristics. (1) The extent of tumor invasion 1. Tumor size: In the absence of regional lymph node metastasis and distant metastasis, the larger the primary focus and the more severe the local infiltration, the worse the prognosis. 2. Axillary lymph node metastasis: the prognosis is good when there is no metastasis in axillary lymph nodes, but poor when there is metastasis. And the more the number of metastases, the worse the prognosis. The prognosis is poor if the metastasis location is high. 3.Distant metastasis: Most of them die in about 1 year. (2) Pathological type of tumor, differentiation degree, aggressiveness of tumor and immunity of host to tumor are important factors affecting prognosis. Special type of breast cancer has better prognosis than non-special type, non-invasive cancer of non-special type has better prognosis than invasive cancer, and well-differentiated tumors have better prognosis than poorly differentiated ones. Some tumors are highly malignant and can appear necrosis when growing rapidly. The seriousness of tumor necrosis indicates the aggressiveness of tumor and poor prognosis. (C) Clinical staging TNM staging is familiar to clinicians, and the prognosis is poor with high stage. However, two points need to be recognized: first, in terms of staging, the presence or absence of metastasis in axillary lymph nodes is more important than the size of tumor; second, clinical axillary lymph node examination for metastasis is often inaccurate. (Steroid hormone receptor measurement can not only be used as a reference for choosing hormone therapy, but also as an indicator for estimating prognosis, the prognosis of patients with positive receptors is better than that of those with negative receptors. Among estrogen receptors and progesterone receptors, progesterone receptors are more important, and the prognosis of those who are positive for both is better than that of those who are positive for one or negative for both. Metastasis and spread】 Similar to a few types of tumors, such as thyroid cancer, the natural course of breast cancer is usually long. The average time for breast cancer cells to multiply is 90 days, and it takes 7-8 years for the tumor to reach a sphere of 1 cm in diameter after more than 30 times of multiplication from the first cell malignancy. The cause of breast cancer is not fully understood, and the best way to reduce mortality is early detection and early treatment. Surgery and radiotherapy alone can cure most cases before metastasis occurs. Once metastasis occurs, aggressive treatment can only cure a small percentage of patients, so understanding the natural course of breast cancer helps to choose the best treatment for breast cancer. It helps to choose the best option to treat breast cancer. Expansion of breast cancer can be direct to the periphery and can be via lymphatic tract and blood stream. The lymph nodes are supposed to be the first barrier to prevent cancer cells from escaping from the primary tumor, and if cancer cells can pass through the lymph node barrier, they usually involve the supraclavicular lymph nodes, which then invade the veins and enter the bloodstream. In addition to the axillary lymph nodes, the tumor can also involve the parasternal lymph nodes, mostly between the second and third or fourth ribs, and more so when the tumor is located in the inner half of the breast and the areola area, from where the cancer can then involve the mediastinal lymph nodes. Breast cancer cells can also directly invade blood vessels and cause distant metastases. The intercostal collateral branches may enter the pulmonary circulation through the internal thoracic vein and enter the ipsilateral innominate vein. The veins of the deep breast tissue, pectoral muscle and chest wall converge into the axillary vein and enter the subclavian vein and the innominate vein, which is an important route for pulmonary metastasis. The intercostal vein flows into the odd vein and the hemi-odd vein, and finally enters the lung through the superior vena cava. Therefore, some patients have metastases in the skull, spine, and pelvis before metastases in the vena cava system (e.g., lung) occur. It has long been recognized that breast cancer can have distant metastases at the time of presentation, although they are not yet clinically detectable, which forms the theoretical basis for the administration of conservative chemotherapy. Today, it is possible to estimate the risk of distant micro-metastases based on the size of the tumor, the number of lymph nodes involved, and various other biological features.